What Everybody Needs To Know About Fractions On The CSET

Adding and subtracting fractions is something you must know how to do if you are going to pass the CSET Multiple Subjects exam.

Adding and Subtracting Fractions

To add or subtract fractions, the denominators must be the same. You then add or subtract the numerators.

Example:

But how do we add or subtract fractions that do not have the same denominator?

You must make the denominators the same by changing to equivalent fractions. If you multiply both the numerator and denominator by the same number, the value of the fraction does not change.

What number should I choose as the common denominator?

Choose a common multiple of the original denominators. Choose their lowest common multiple.

Examples: